Method of making integrated stator, brushless direct-current motor of radial core type double rotor structure using the integrated stator, and method of making the same

ABSTRACT

Provided are a radial core type brushless direct-current (BLDC) motor and a method of making the same, having an excellent assembly capability of division type stator cores in a double rotor structure BLDC motor. The BLDC motor includes a rotational shaft, an integrated double rotor including an inner rotor and an outer rotor, and a rotor supporter wherein a trench type space is formed between the inner rotor and the outer rotor, and an end extended from the inner rotor is connected with the outer circumferential surface of a bushing combined with the rotational shaft, and an integrated stator wherein one end of the stator is disposed in the trench type space and an extension axially extended from the other end of the integrated stator is fixed to the housing of the apparatus. In the integrated stator, U, V, W phase coil assemblies are formed of a number of core groups including a number of division type cores, wherein for each phase coil assembly, the division type core groups of the U, V, W phase coil assemblies are alternately disposed in an annular form in sequence of the phases, and the respective division type core groups are integrally formed into a single body in annular form by a stator support.

REFERENCE TO RELATED APPLICATION

This patent application is being filed as a Divisional patentapplication of Ser. No. 11/529,241, filed 29 Sep. 2006, currentlypending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of making an integratedstator, a radial core type brushless direct-current (BLDC) motor usingthe integrated stator, and a method of making the radial core typebrushless direct-current (BLDC) motor, and more particularly, to abrushless direct-current (BLDC) motor having a radial core type doublerotor structure which can greatly enhance productivity of assembling astator in which coils are sequentially wound on a plurality of divisiontype stator cores in a continuous winding method, and a plurality ofinterconnected stator core assemblies are automatically located and setusing positioning grooves which are formed in a mold itself to then beinjection-molded at an insert molding mode.

2. Description of the Related Art

BLDC motors are classified into a core type (or radial type), which hasa generally cup-shaped (or cylindrical) structure, and a coreless type(or axial type), according to whether or not a stator core exists.

BLDC motors of a core type structure are classified into an internalmagnet type including a cylindrical stator where coils are wound on anumber of protrusions formed on the inner circumferential portionthereof in order to form an electronic magnet structure, and a rotorformed of a cylindrical permanent magnet, and an external magnet typeincluding a stator where coils are wound up and down on a number ofprotrusions formed on the outer circumferential portion thereof, and arotor formed of a cylindrical permanent magnet on the outer portion ofwhich multiple poles are magnetized.

In a conventional external magnet type BLDC motor, a main path of amagnetic flux is a magnetic circuit which forms a closed circuitstarting from a permanent magnet of a rotor and proceeding again towardthe permanent magnet and a yoke via a gap and the stator core of astator.

In a conventional internal magnet type BLDC motor, a plurality ofT-shaped core portions on a stator core around which coils are wound,protrude inwards. Also, the inner longitudinal sections of therespective core portions form a circle of a predetermined diameter tothereby make the core portions form a cylinder. Also, a rotor having acylindrical permanent magnet including a rotational shaft, or aring-shaped permanent magnet attached to a cylindrical yoke including acentral rotational shaft, is mounted in the inner portion of thecylinder surrounded by the core portions. The internal magnet type BLDCmotor rotates in the same manner as that of the external magnet typeBLDC motor.

The magnetic circuit in the above-described core type BLDC motor has asymmetrical structure in the radial direction around the rotationalshaft. Accordingly, the core type BLDC motor has less axial vibrationalnoise, and is appropriate for low-speed rotation. Also, since a portionoccupied by a gap with respect to the direction of the magnetic path isextremely small, a high magnetic flux density can be obtained even if alow performance magnet is used or the quantity of magnet to be used isreduced. As a result, a big torque and a high efficiency can beobtained.

However, such a core, that is, a yoke structure causes big loss of ayoke material when fabricating a stator. In addition, a special-purposeexpensive dedicated winding machine should be used for winding coilsaround the yoke during mass-production, because the yoke structure iscomplicated. Also, since a mold for fabricating a stator is expensive,initial investment costs become high.

In the core type AC or BLDC motor, especially, in the core motor of theradial type, it is very important factor for determining a competitivepower of motors, to make the stator core configured into a completedivision type, since coils can be wound on division type cores with ahigh efficiency using a general purpose winding machine which is cheaperthan a special-purpose expensive dedicated winding machine. On thecontrary, since a low efficient winding is made using the expansivededicated winding machine, in the case of an integrated stator corestructure, a manufacturing cost for the motors becomes high.

In order to employ the advantages of the axial double rotor type and theradial core type and improve the disadvantages thereof, a radial coretype double rotor structure BLDC motor has been proposed in KoreanPatent No. 432954 to the same applicant.

In the Korean Patent No. 432954, rotors including respective permanentmagnets are disposed in both the inner and outer sides of a stator coreto thereby form flow of a magnetic path by the permanent magnets and therotor yoke. It is thus possible to divide the stator core completelyinto a plurality of stator core portions. Accordingly, productivity ofthe stator core and power of the motor can be greatly heightened throughan individual coil winding process.

Moreover, in the Korean Patent No. 432954, a plurality of division typecore assemblies around which coils have been wound are prepared, andthen the plurality of division type core assemblies around which coilshave been wound are arranged and fixed on a printed circuit board (PCB).Then, the coils are connected and thereafter the plurality of divisiontype core assemblies around which coils have been wound are molded in anannular form using an insert molding process using a thermosettingresin, to thus prepare an integrated stator.

However, when a plurality of individual cores are integrally assembledto thereby mutually connect coils, in the Korean Patent No. 432954, anassembling structure and method of the stator which can be effectivelyassembled have not been presented.

As described above, the coil winding of the individual division core ismore greatly excellent in its productivity than that of the case ofusing the integrated (that is, single) core when implementing the statorcore into a plurality of division type cores. However, there is astructural problem of lowering a productivity and durability thereofwhen the plurality of division type cores are assembled.

Taking such points into consideration, Korean Patent No. 545848discloses a structure of enhancing an assembly productivity of a stator,including an annular core support plate which a plurality of stator coreassemblies around a bobbin of which coils are wound are accommodated inand supported to at a regular interval, and a plurality of coils arewired by electric phases, and an automatic positioning/supporting unitfor automatically positioning and supporting the plurality of statorcore assemblies in and to the core support plate.

In the Korean Patent No. 545848, a plurality of division type coreassemblies which are obtained by winding coils around each division typecore are assembled in the core support plate, and the respective coreassemblies are electrically interconnected in the core support plate. Inthis case, since the wound coils should be connected to connection pinsand the connection pins should be coupled to conductive lines formed inthe core support plate in the bobbin of each division type core, anassembly productivity is lowered.

Therefore, preferably, it is required to integrate a plurality of statorcores in which coils are wound with an insert molding process using athermosetting resin without using the annular core support plate asdescribed above.

In the meantime, a general large-sized motor has a structure in which aplurality of stator poles and a plurality of rotor poles are combinedwith each other. In the case of a division core type, a continuouswinding which is made on a number of groups of cores composed of aplurality of division type cores is more preferable than an individualwinding/assembly which is made on a plurality of division type cores inview of an assembly productivity.

However, the known general purpose winding machine has a structure ofwinding coils as a single bobbin is mounted in a single spindle to thenmake the spindle rotate. Accordingly, continuous windings cannot be madeon a number of groups of cores composed of a plurality of division typecores, or a plurality of division type cores.

In the meantime, a stator core is generally made by molding a pluralityof silicon steel plates of 0.35-0.5 mm thick in a predetermined shape,and laminating the molded results. In the case of an integrated coretype, a magnetic flux density is not uniform at the air gap due to theinfluences of slots for winding coils to thereby generate a coggingtorque phenomenon and a torque ripple phenomenon for which the torque isnot regular. In order to reduce the cogging torque and the torqueripple, a number of slots should be formed in the stator cores, orauxiliary salient poles or auxiliary slots should be formed in thestator core. Otherwise, the stator core employs a skew structure.

However, the integrated stator core employing the skew structure has theproblem that its coil winding is more difficult than that of the statorcore which does not adopt the skew structure. When a skew is given to acore in the division type stator core structure so that the divisiontype core itself is divided to form a structure of a motor, that is, astator, it is impossible to perform coupling between the cores.

In the meantime, in the case of the motor disclosed in the Korean PatentNo. 545848, a plurality of cooling holes for cooling the coils of thestator inserted between the rotor supporters are formed in the rotorsupporters. The rotor supporters and bushings are connected therebetweenwith a plurality of radially extending ribs.

However, a plurality of radially extending ribs connecting between therotor supporters and the bushings do not have enough support strengthand thus there is a need to reinforce the plurality of radial ribs. Theplurality of simple cooling holes for cooling the coils of the statorformed in the rotor supporters do not induce an effective flow of theair.

SUMMARY OF THE INVENTION

To solve the above problems, it is an object of the present invention toprovide a method of making an integrated stator having an excellentassembly productivity, a brushless direct-current (BLDC) motor of aradial core type double rotor structure using the integrated stator, anda method of manufacturing the brushless direct-current (BLDC) motor, inwhich a plurality of interconnected stator cores are automaticallypositioned using a positioning structure which is formed in a molditself to then be injection-molded using a thermosetting resin.

It is another object of the present invention to provide a brushlessdirect-current (BLDC) motor and a method of manufacturing the same,which minimizes inconveniences caused when a number of division typestator cores are located and set in a mold without having a separatepositioning component, in which a number of division type stator corescorresponding to respective phases are sequentially wound with a singlecoil and interconnected with one another, using a sequential windingmethod, and simultaneously mutual link connection is achieved by anunevenness structure between adjoining division type core bobbins when anumber of division type core bobbins around which coil is wound aretemporarily assembled in the mold for an insert molding process.

It is still another object of the present invention to provide abrushless direct-current (BLDC) motor having a skew core structurestator in which a coil winding process is easy since a division typecore structure is employed even though the skew core structure has beenemployed, and each skew core can be integrally molded in an insertmolding process using a thermosetting resin so as to be easilyassembled, thereby reducing a cogging torque and noise/vibration.

It is yet another object of the present invention to provide a brushlessdirect-current (BLDC) motor having an integrated double rotor structurewhich can enhance a cooling performance, in which a cooling hole isformed to have a cross-sectional area as wide as possible, vertically tothe circumferential direction of a rotor supporter and a rib whichconnect inner and outer rotors and bushings, and a change in the size ofthe cooling hole is alternately given by design, to thereby reinforce asupport strength of the rotor supporter and rib and simultaneouslygenerate a turbulent flow and induce a flow of cooled air into amagnetic gap, that is, an air gap between the upper space of the statorand the inner and outer rotor and stator.

It is yet still another object of the present invention to provide abrushless direct-current (BLDC) motor having a stator structure capableof enhancing a cooling performance, in which a support is formed using athermosetting resin along a semi-circular curve of a coil wound on abobbin when a stator is integrally molded via an insert molding methodusing the thermosetting resin to thereby increase a contact areacontacting air and simultaneously generate a turbulent flow duringrotation of a rotor.

It is a further object of the present invention to provide a brushlessdirect-current (BLDC) motor having a stator structure capable ofenhancing a cooling performance, in which a number of grooves includinga number of bolt fitting holes and bolt positioning holes and a numberof radial ribs are included in an extension for fixing a stator, tothereby maintain a support intensity, reduce a material cost, seeklightweight, and generate a turbulent flow together with cooling bladesof an inner rotor during rotation of the rotor.

It is a still further object of the present invention to provide abrushless direct-current (BLDC) motor having a depression type rotorstructure in which an axial coupler of a rotor combined with a rotatingaxis is disposed at the center of gravity of the inner side of therotor, to thereby suppress vibration from occurring during rotation ofthe rotor to the minimum, simultaneously to shorten an axial length of amotor to the minimum, and effectively heighten a cooling efficiency of astator and the rotor.

It is a yet further object of the present invention to provide abrushless direct-current (BLDC) motor having a stator structure in whicha number of annular ribs are formed on the upper surface of a statorwhen the stator is injection-molded using a thermosetting resin, tothereby prevent a crack which can occur during the injection moldingfrom being propagated.

It is a still yet further object of the present invention to provide abrushless direct-current (BLDC) motor of a radial core type for awashing machine in which a double rotor and a stator are integrallymolded by an insert molding method using a thermosetting resin,respectively, to thereby heighten durability, reliability and waterproofcapability.

It is another further object of the present invention to provide abrushless direct-current (BLDC) motor of a radial core type having anexcellent safety from fire risk since a thermosetting resin enclosing adouble rotor and a stator is a heat-resistant material.

To accomplish the above object of the present invention, according to anaspect of the present invention, there is provided a brushlessdirect-current (BLDC) motor having a radial core type double rotorstructure using a three-phase driving mode, the BLDC motor comprising: arotational shaft which is rotatably mounted in a housing of anapparatus; an integrated double rotor including an inner rotor and anouter rotor in which a plurality of N-pole and S-pole magnets aredisposed alternately in annular form on different concentriccircumferences in each rotor, and opposing magnets with a predetermineddistance between the inner and outer rotors are disposed to haveopposite polarities, and a rotor supporter which is molded using athermosetting resin, so that the respective inner and outer rotors areannularly integrated except for the opposing magnet surfaces of theinner and outer rotors, a trench type space is formed between the innerrotor and the outer rotor, and an end extended from the inner rotor tothe central portion is connected with the outer circumferential surfaceof a bushing combined with the rotational shaft; and an integratedstator wherein U, V, W phase coil assemblies formed of a number of coregroups including a number of independent division type cores on theouter portion of which bobbins are respectively formed, wherein for eachphase coil assembly, coils are sequentially wound around each divisiontype core so that short jump wires are connected between the divisiontype cores in each division type core group, and long jump wires areconnected between the division type core groups, wherein the divisiontype core groups of the U, V, W phase coil assemblies are alternatelydisposed in an annular form in sequence of the phases, wherein therespective division type core groups are integrally formed into a singlebody in annular form by a stator support except for the inner and outerside surfaces of the division type cores via an insert molding methodusing a thermosetting resin, and wherein one end of the integratedstator is disposed in the trench type space between the inner and outerrotors and an extension axially extended from the other end of theintegrated stator is fixed to the housing of the apparatus.

Preferably, the rotor supporter comprises: a number of large-size holesand small-size holes which are alternately disposed in order to guideexternal air to a trench type space opposing an end of the statorbetween the inner and outer rotors in the inner side direction the innerrotor and in a magnetic gap direction between the inner and outer rotorsand the stator, and a number of radial ribs which are disposed as axialcouplers surrounding the outer circumferential surface of the bushingfrom the inner rotor to the central portion thereof.

Preferably, a number of grooves are periodically formed at portionswhere an annular molding support supporting the inner rotor among therotor supporters, meets a number of the large-size holes along thecircumferential direction.

Further, when the axial coupler is disposed in the center of gravity ofthe double rotor, vibration during rotation of the rotor can beminimized.

Further, the rotor in the motor is integrally formed with the rotorsupporter at the lower portion of the inner rotor and/or outer rotor,and further comprises a number of cooling blades having any one of: alinear fan which is congruent with the axial direction for producingwind during rotation of the rotor; a Sirocco fan having circular groovesalong the rotational direction of the rotor; a turbo fan in whichgrooves are formed in the opposite direction to the rotational directionof thereto; and a slanted fan which is slanted with respect to the axialdirection.

Further, when a number of the division type cores are skewed within onepitch range which is defined as 360°/slot number, a cogging torque canbe reduced.

Preferably, the motor is made of a 24-pole-27-core structure, whereinthe stator is configured that U, V, W phase coil assemblies formed ofthree core groups including three division type cores on the outerportion of which bobbins are respectively formed, and wherein for eachphase coil assembly, the division type core groups of the U, V, W phasecoil assemblies are alternately disposed in an annular form in sequenceof the phases.

Here, when the motor is applied to a washing machine, the rotationalshaft is connected with a drum or a tub rotatable about its longitudinalaxis for holding clothes to be washed in a washing machine.

According to another aspect of the present invention, there is provideda brushless direct-current (BLDC) motor having a radial core type doublerotor structure using a three-phase driving mode, the BLDC motorcomprising: an integrated double rotor including an inner rotor and anouter rotor in which N-pole and S-pole magnets of twenty-four poles aredisposed alternately in an annular form on different concentriccircumferences in each rotor, and opposing magnets with a predetermineddistance between the inner and outer rotors are disposed to haveopposite polarities, and a rotor supporter which is molded using athermosetting resin, so that the respective inner and outer rotors areannularly integrated except for the opposing magnet surfaces of theinner and outer rotors, and a trench type space is formed between theinner rotor and the outer rotor, so that the rotor supporter is extendedfrom the inner rotor to an axial coupler surrounding a bushing; arotational shaft whose one end is coupled with the bushing and other endis rotatably mounted in a housing of an apparatus; and an integratedstator wherein U, V, W phase coil assemblies formed of three core groupsincluding three independent division type cores on the outer portion ofwhich bobbins are respectively formed, wherein for each phase coilassembly, the division type core groups of the U, V, W phase coilassemblies are alternately disposed in an annular form in sequence ofthe phases, wherein the respective division type core groups areintegrally formed into a single body in annular form by a stator supportexcept for the inner and outer side surfaces of the division type coresvia an insert molding method using a thermosetting resin, wherein oneend of the integrated stator is disposed in a trench type space betweenthe inner and outer rotors, and wherein nine division type coresrespectively included in the U, V, W phase coil assemblies are mutuallyconnected by the sequentially wound coils.

According to still another aspect of the present invention, there isprovided a double rotor type motor for use in a washing machine, thedouble rotor type motor comprising: an integrated double rotor includingan inner rotor and an outer rotor in which a plurality of N-pole andS-pole magnets are disposed alternately in annular form on differentconcentric circumferences in each rotor, and opposing magnets with apredetermined distance between the inner and outer rotors are disposedto have opposite polarities, and a rotor supporter which is molded usinga thermosetting resin, so that the respective inner and outer rotors areannularly integrated except for the opposing magnet surfaces of theinner and outer rotors, a trench type space is formed between the innerrotor and the outer rotor, so that the rotor supporter is extended fromthe inner rotor to an axial coupler surrounding a bushing; a rotationalshaft one end of which is coupled with the bushing and two points of theother end of which are rotatably mounted in a housing of the washingmachine; and an integrated stator wherein for each phase, coils aresequentially wound around each division type core in a sequentialwinding method, wherein the respective division type cores areintegrally formed into a single body in an annular form by a statorsupport except for the inner and outer side surfaces of the divisiontype cores via an insert molding method using a thermosetting resin,wherein one end of the integrated stator is disposed in the trench typespace between the inner and outer rotors and an extension axiallyextended from the other end of the integrated stator is fixed to thehousing of the washing machine, and wherein said axial coupler isdisposed in a center of gravity of the double rotor.

According to yet another aspect of the present invention, there isprovided a method of manufacturing a brushless direct-current (BLDC)motor having a radial core type double rotor structure using athree-phase driving mode, the BLDC motor manufacturing method comprisingthe steps of: integrally molding a number of division type core of anI-shape by an inset molding using a thermosetting resin to obtain anumber of division type core bobbins around which coils are wound,respectively and which include first and second flanges at both endsthereof, and first and second coupling protrusions which are located inthe lower portions of the first and second flanges; preparing three setsof coil assemblies corresponding to respective U, V, W phases includinga number of the division type core bobbins in which coils aresequentially continuously wound between the first and second flanges ofthe respective division type core bobbins; temporarily assembling thefirst and second coupling protrusions of the respective division typecore bobbins included in the three sets of the coil assemblies in a moldwhere a number of pairs of positioning grooves are formed in oppositionto inner and outer walls of annular grooves; preparing an integratedstator by forming the coil assemblies in an annular form by an insertmolding method using a thermosetting resin, except for the inner andouter side surfaces of each division type core; and assembling theintegrated stator so as to be positioned between the double rotors inwhich an inner rotor and an outer rotor are aligned in a radial type.

Preferably, the motor is made of a 24-pole-27-core structure, andwherein the three-set coil assemblies preparation step comprises thesub-steps of: inserting eight division type core connection jigs betweenthe nine division type core bobbins and assembling three core/jigassemblies formed by connecting the nine division type core bobbins inseries; sequentially winding coils around each division type core bobbinin the three core/jig assemblies so that short jump wires are connectedbetween the division type core bobbins in each division type core groupand long jump wires are connected between the division type core groups,for the three division type core groups including the three divisiontype core bobbins which are adjacent to each other; and separating thedivision type core connection jigs from the coil-wound core/jigassemblies and thus preparing three sets of coil assembliescorresponding to the respective U, V, W phases.

Here, the step of temporarily assembling a number of the division typecore bobbins included in the three sets of coil assemblies in the mold,comprises the sub-steps of: disposing the division type core group ofeach phase in the mold where twenty-seven pairs of positioning fixinggrooves are formed in sequence of the phases so as to then betemporarily assembled, for the three division type core groups includingthe three division type core bobbins which are adjacent to each other.

Here, the motor has a double rotor/single stator structure, and when thestator core is formed of a division type structure, the interval betweenthe adjacent division type cores is set wider than the magnetic gapbetween the inner and outer rotors and the stator.

As described above, the present invention employs a double rotorstructure in a radial core type BLDC motor, in which a number ofdivision type core assemblies are automatically positioned and fixed,using a positioning structure formed in a mold itself when a stator coreis perfectly divided into divided cores, and then is injection-molded byan insert molding method using a thermosetting resin, to therebyassemble a number of divided cores without using a separate core supportplate and thus greatly enhance an assembly productivity.

In addition, in the double rotor structure of the present invention, acooling hole is formed to have a cross-sectional area as wide aspossible, vertically to the circumferential direction of a rotorsupporter and a rib which connect inner and outer rotors and bushings,and a change in the size of the cooling hole is alternately given bydesign, to thereby reinforce a support strength of the rotor supporterand rib and simultaneously generate a large amount of wind and aturbulent flow and induce a flow of cooled air into a magnetic gapbetween the upper space of the stator and the inner and outer rotor andstator. Accordingly, heat generated from the rotor and the stator can beeffectively cooled.

Further, in a stator structure according to the present invention, asupport is formed using a resin along a semi-circular curve of a coilwound on a bobbin when a stator is integrally molded via an insertmolding method using a thermosetting resin to thereby increase a contactarea contacting air and simultaneously generate a turbulent flow duringrotation of a rotor, to thereby be capable of enhancing a coolingperformance.

Further, in a stator structure according to the present invention, anumber of throughholes including a number of bolt fitting holes and boltpositioning holes and a number of radial ribs are included in a bearinghousing, to thereby maintain a support intensity, reduce a materialcost, seek lightweight, and generate a turbulent flow together withcooling blades of an inner rotor during rotation of the rotor, and tothus be capable of enhancing a cooling performance.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the present invention willbecome more apparent by describing the preferred embodiments thereof inmore detail with reference to the accompanying drawings in which:

FIG. 1A is a partially cut-out cross-sectional view cut along the axialdirection of a brushless direct-current (BLDC) motor of a radial coretype having a structure of double rotors according to a first embodimentof the present invention;

FIG. 1B is a cross-sectional view cut along the circumferentialdirection of the brushless direct-current (BLDC) motor of a radial coretype having a structure of double rotors according to the firstembodiment of the present invention, in order to illustrate a magneticcircuit;

FIG. 1C is a cross-sectional view of washing machine using the brushlessdirect-current (BLDC) motor according to the first embodiment of thepresent invention;

FIGS. 2A through 2C are a perspective view, a plan view, and a rear viewof a stator which is used in the present invention, respectively;

FIG. 3A is a perspective view of a division type core according to thepresent invention;

FIGS. 3B and 3C are a perspective view of one side and the other side ofa divided core in which a bobbin is combined according to the presentinvention, respectively;

FIG. 4A is a plan view of a division type skew core according to thepresent invention;

FIGS. 4B and 4C are a rear and plan views of a divided skew core inwhich a bobbin is combined according to the present invention,respectively;

FIG. 5A is a circuit diagram of a three-phase driving mode stator coilof a 24-pole-27-core motor in which the present invention is applied;

FIG. 5B is a circuit diagram for explaining an arrangement sequence atthe time of assembling a stator core of FIG. 5A;

FIGS. 6A through 6C are a front view, a left side view, and a right sideview showing a connection jig connecting divided cores according to thepresent invention, respectively;

FIG. 6D is a cross-sectional view cut along a line C-C of FIG. 6C;

FIGS. 7A and 7B are a front view of a core/jig assembly showing thestate where the connection jig and the divided core are assembled, and aperspective view schematically showing a continuous winding machine,respectively;

FIGS. 8A and 8B are diagrams for illustrating the operation in which thecoil winding is made while securing the short jump wire between adjacentcores in a core group, respectively;

FIGS. 8C and 8D are diagrams for illustrating the operation in which thecoil winding is made while securing the long jump wire between adjacentcores in the core group, respectively;

FIG. 9A is a diagram for illustrating a mold structure forinjection-molding a plurality of divided core assemblies using an insertmolding mode according to the present invention;

FIG. 9B is a perspective view showing the state where a plurality ofdivided core assemblies are arranged in an annular shape for an insertmolding mode;

FIGS. 10A through 10E are a perspective view of the upper side, apartially cut-out front view, a plan view, a rear view, and acircumferentially sectionalized perspective view of a rotor according tothe present invention, respectively;

FIGS. 11A through 11D are a partially cut-out front view of a rotor forillustrating the flow of the air according to the rotation location ofthe rotor, respectively;

FIGS. 12A through 12E are diagrams showing a fan blade which can beapplied in a rotor, respectively;

FIGS. 13A and 13B are perspective views illustrating the inner and outerrotor assemblies and an involute serration structure which are used forassembly of the double rotors of the present invention, respectively;

FIG. 14 is an axial sectional view of a BLDC motor of a radial core typehaving a structure of double rotors according to a second embodiment ofthe present invention;

FIG. 15A is a plan view of double rotors shown in FIG. 14;

FIGS. 15B and 15C are a cross-sectional view and a rear view of thedouble rotors of FIG. 15A which is cut along a line X-X, respectively;

FIG. 16A is a plan view of a stator shown in FIG. 14; and

FIGS. 16B and 16C are a cross-sectional view and a rear view of thestator of FIG. 16A which is cut along a line Y-Y.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings.

I. First Embodiment A. Overall Structure of Motor

FIG. 1A is a partially cut-out cross-sectional view cut along the axialdirection of a brushless direct-current (BLDC) motor of a radial coretype having a structure of double rotors according to a first embodimentof the present invention, FIG. 1B is a cross-sectional view cut alongthe circumferential direction of the brushless direct-current (BLDC)motor of a radial core type having a structure of double rotorsaccording to the first embodiment of the present invention, in order toillustrate a magnetic circuit, and FIG. 1C is a cross-sectional view ofwashing machine using the brushless direct-current (BLDC) motoraccording to the first embodiment of the present invention.

In the embodiment shown in FIGS. 1A and 1C, a brushless direct-current(BLDC) motor 1 of a radial core type having a structure of double rotorsis installed in especially, the lower portion, i.e., housing 10 of anouter tub 112 in a washing machine 110 and has a proper structure ofmaking a perforated tub 114 of the washing machine 110 rotate in aforward/reverse direction. The perforated tub 114 is disposed insideouter tub 112 to hold clothes to be washed and is connected to arotational shaft 9 of the BLDC motor 1. The perforated tub 114 mayinclude an agitator or a pulsator. More particularly, the perforated tub114 spins around its longitudinal axis during the spin-cycle of thewashing machine 110 to remove water from the interior of the tub.However, the present invention is not limited thereto. For example, theBLDC motor is installed at the back side of a washing machine and has aproper structure of making a washing drum of the washing machine rotatein a forward/reverse direction. In addition, the BLDC motor can beapplied to the other instruments other than the washing machine.

The BLDC motor 1 of the radial core type double rotor structureaccording to the first embodiment of the present invention includes astator 3 in which a plurality of division cores 30 are integrally formedby an annular stator supporter 2 which is manufactured by an insertmolding method using a thermosetting resin after coils have been woundaround the outer circumference of bobbins (not shown), an inner rotor 4which has predetermined magnetic gaps G1 and G2 on the inner and outercircumferential portions of the stator 3 in which a plurality of magnets4 a and ring-shaped inner yokes 4 b are disposed in an annular form, anouter rotor 5 in which a plurality of magnets 5 a and ring-shaped outeryokes 5 b are disposed, and a rotational shaft 9 whose one end isconnected to the central portion of a rotor support frame 6 through aninvolute serration bushing 7 and whose other end is rotatably supportedthrough a pair of bearings 8 in the housing 10.

In the stator 3, a plurality of the division cores 30 which have beencompletely divided are integrally molded by an annular stator supporter2 in an annular form. The stator supporter 2 includes an extension 2 aextended toward the inner side thereof as shown in FIGS. 2A to 2C. Thestator supporter 2 is supported by an anchoring bolt 11 in for example,the housing 10 of a washing machine 110. In this case, the bearings 8are installed at the housing 10, for example, the outer tub 112 of apulsator type washing machine and rotatably supports a double rotor 50combined in the rotational shaft 9 through the bushing 7. In this case,the rotational shaft 9 is rotatably supported in the outer tub 112 ofthe washing machine 110, and is extended in order to operate theperforated tub (or washing tub) on the floor of which a pulsator isinstalled and which accommodates a laundry, or is extended in order tooperate the drum of a drum-type washing machine, or the agitator of anagitator-type washing machine.

Therefore, the BLDC motor 1 forms the radial core type motor includingthe double rotor 50 in which the inner rotor 4 and the outer rotor 5 aresupported by the rotor support frame 6, and the single stator 3.

B. Structure of Stator and Manufacturing Process

FIGS. 2A through 2C are a perspective view, a plan view, and a rear viewof a stator which is used in the present invention, respectively. FIG.3A is a perspective view of a division type core according to thepresent invention. FIGS. 3B and 3C are a perspective view of one sideand the other side of a division type core in which a bobbin is combinedaccording to the present invention, respectively.

Moreover, FIG. 5A is a circuit diagram of a three-phase driving modestator coil of a 24-pole-27-core motor in which the present invention isapplied, and FIG. 5B is a circuit diagram for explaining an arrangementsequence at the time of assembling a division type core around whichstator coils are wound of FIG. 5A.

The BLCD motor of the present invention can be implemented into forexample, a 24-pole-27-core structure in the case of being applied to alarge capacity washing machine. In this case, the inner rotor 4 and theouter rotor 5 are adhered to the outer side surface and the inner sidesurface of the annular inner and outer yokes 4 b and 5 b formed of24-pole magnets 4 a and 5 a, respectively. The integrated stator 3including twenty-seven division cores 30 (FIG. 3A) is inserted into theannular space between the double rotors.

Hereinbelow, the manufacturing process of the integrated stator 3including the twenty-seven division cores 30 will be illustratedschematically first and then will be described in detail for eachspecific process.

First, twenty-seven division cores 30 (FIG. 3A) are molded at the outerside surface by an insert molding mode using a thermosetting resin, tothus form an insulation bobbin 20, as shown in FIGS. 3B and 3C. In thisstate, coils 33 are wound around the outer circumference of the bobbin20. Copper (Cu) is used as the general material of the coil. However, itis possible to use aluminium (Al) where the specific gravity is ⅓ incomparison with Cu in order to reduce the weight of the motor, and thecost is relatively cheaper than Al.

Thereafter, twenty-seven division type core assemblies 300 (FIG. 9B)around which coils are wound are temporarily assembled in an annularform inside the grooves 32 of the mold 31 and molded using athermosetting resin, as shown in FIG. 9A, and accordingly the annularintegrated stator 3 shown in FIGS. 2A to 2C is obtained.

Firstly, when the stator 3 operates at a three-phase driving mode, asshown in FIG. 5A, twenty-seven division type core assemblies 300 aredivided into three sets of coil assemblies 33 a-33 c in which a statorcoil 33 is sequentially wound around nine division cores u1-u9, v1-v9,and w1-w9 for each phase of U, V, W. The respective coil assemblies 33a-33 c, that is, the nine division cores u1-u9, v1-v9, and w1-w9 formthree core groups G1-G3, G4-G6, and G7-G9. In this case, the inputs ofthe division cores u1, v1, and w1 positioned in a first stage of therespective core groups G1-G3, G4-G6, and G7-G9 become the inputterminals of the respective U, V, W phases and thus are connected to theterminal blocks 12 (FIG. 2A). The outputs from the division cores u9,v9, and w9 positioned in the final stage are mutually connected and formthe neutral point (NP).

The twenty-seven division cores u1-u9, v1-v9, and w1-w9, are formed intothree sets of coil assemblies 33 a-33 c in which coils are sequentiallywound around the nine division cores u1-u9, v1-v9, and w1-w9 so as toinclude three core groups G1-G3, G4-G6, and G7-G9, respectively.Thereafter, when the coil assemblies 33 a-33 c are temporarily assembledin the annular grooves 32 of the mold 31, as shown in FIG. 5B, the threedivision cores are formed into a group and the core groups G1-G3, G4-G6,and G7-G9 of the respective U, V, W phases are alternately disposed insequence of the respective phases. That is, when the driving current isswitched and applied to the respective U, V, W phases, the nine divisioncore groups G1-G9 are arranged in sequence of G1-G4-G7-G2-G5-G8-G3-G6-G9so that the rotation of rotors 4 and 5 is made.

As described above, for example, the stator core group G1-G3 of the Uphase, 3 is composed of three groups which become interconnected inwhich three division cores u1-u3, u4-u6, and u7-u9 in which the coils 33are wound around the respective insulation bobbins 20 form the groups.

In this case, since the adjacent division cores, for example, u1 and u2,and u2 and u3 are disposed close to each other, in the nine divisioncores u1-u9, they are interconnected via short jump wires J1 whoselength is relatively short. Because the assembly of the core groups ofeach phase is alternately made, as described above, in the core betweenthe respective groups G1-G3, for example, u3 and u4, and u6 and u7through the relatively long jump wires J2.

Successively when the stator coil 33 which will be described later acoil is sequentially wound around the nine division cores u1-u9, v1-v9,and w1-w9, the short jump wires J1 are secured between the adjacentdivision cores in the group, and the long jump wires J2 are securedbetween the division cores among the groups.

As shown in FIG. 3A, the division core 30 is formed of an I-shaped form.As shown in FIGS. 3B and 3C, a bobbin 20 which is made of an insulatingmaterial such as a plastic material is combined with the outercircumferential portion of the I-shaped division type core 30. Thebobbin 20 is formed of a rectangular box portion 21 around which a coilis wound and which is formed in the middle portion, and inner and outerflanges 22 a and 22 b which are formed by being bent from the inner andouter sides of the rectangular box portion. The rectangular box portionbetween the flanges 22 a and 22 b is the space around which the coil 33can be wound.

In the I-shaped division type core 30, the inner and outer flanges 30 band 30 c are bent and extended to the inner and outer sides of thelinear type body 30 a, respectively. The inner flange 30 b is roundedinwards, so as to maintain a predetermined interval from the annularinner and outer rotors (not illustrated), and the outer flange 30 c isrounded outwards (FIG. 3A). In this case, it is preferable that theouter flange 30 c has to be formed relatively larger than the innerflange 30 b.

Moreover, the bobbin 20 and the I-shaped division core 30 is preferablyassembled by an insert molding mode using a thermosetting resin in anintegral form. However, it is not limited thereto, but can be assembledusing the well-known modes.

In the case of the inner and outer flanges 22 a and 22 b of the bobbin20, it is preferable that the outer flange 22 b has to be formedrelatively larger than the inner flange 22 a. In order to fix theoutgoing line of the coil 33 which has been wound around the bobbin,insertion grooves 26 a and 26 b for fixing coils are formed in the upperportion of the inner and outer flanges 22 a and 22 b. Moreover, a pairof inner and outer protrusions 24 a and 24 b are integrally formed onthe outside of the lower portion of the inner and outer flanges 22 a and22 b, in order to guide a plurality of division type core assemblies 300around which the coil 33 is wound so as to be automatically assembledinto fixing grooves 34 a and 34 b for positioning which are formed inthe inner and outer walls of the annular groove 32 in the mold 31.

As shown in FIG. 9A, according to the present invention, twenty-sevenpairs of fixing grooves 34 a and 34 b for position determination intowhich the inner and outer protrusions 24 a and 24 b formed in the bobbin20 of twenty-seven division type core assemblies 300 are inserted andfixed, are formed in the corresponding positions of the inner and outerwalls of the annular groove 32 in the mold 31. For this, steppedportions 35 a and 35 b are formed in the inner and outer walls of theannular groove 32 of the mold 31. The division type core assembly 300shown in FIG. 9A shows a division core in which a coil is not wound forconvenience of explanation.

Therefore, in the present invention, an insert molding process is notperformed at the state where that a plurality of division type coreassemblies are temporarily assembled in an annular core support platewhich includes an automatic positioning/supporting unit in advance inorder to integrate a plurality of the division type core assemblies asin the conventional art. However, the insert molding process can beperformed at the state where a plurality of division type coreassemblies are temporarily immediately assembled into fixing grooves 34a and 34 b for position determination formed in the annular groove 32 inthe mold 31.

Moreover, in the conventional art, a plurality of division type coresare not connected in advance in a sequential winding method, but aplurality of division type core assemblies obtained by winding a coilaround each division type core are assembled in the core support plate,and then the respective division type core assemblies are mutuallyconnected in order to connect the respective division type coreassemblies electrically in the core support plate. In this case, thereare problems that the wound coil should be connected with the connectionpin and then the connection pin should be coupled with the conductionline formed in the core support plate, in order to make the electricalconnection easy in the bobbin of each division core, to accordinglylower an assembly productivity.

However, in the present invention, it is possible to directly assemble aplurality of division type core assemblies 300 with fixing grooves 34 aand 34 b for position determination in the mold 31, to thereby removethe core support plate for temporary assembly.

Moreover, twenty-seven division cores u1-u9, v1-v9, and w1-w9 form threecore groups G1-G3, G4-G6, and G7-G9 for each phase as shown in FIGS. 5Aand 5B. If the core groups G1-G3, G4-G6, and G7-G9 of the respective U,V, W phases are alternately arranged in sequence of the phases and arethen temporarily assembled in sequence of G1-G4-G7-G2-G5-G8-G3-G6-G9, aplurality of the division type core assemblies 300 are formed as shownin FIG. 9B. FIG. 9B does not show the coil wound around the bobbin forconvenience of explanation.

As shown in FIG. 9B, the neighbouring bobbins 20 are designed to contacteach other between a plurality of the division type core assemblies 300.Accordingly, the possibility of being inclined or moved due to thetolerance or the thermal transformation of the components is minimized.Moreover, the whole intensity can be improved after the injectionmolding.

In this case, in the above preferred embodiment, the structure ofdirectly assembling a plurality of division type core assemblies 300 infixing grooves 34 a and 34 b for position determination in the mold 31has been exemplified. However, instead of fixing grooves for positiondetermination, it is possible to perform an insert molding process atthe state where the mutual link connection is accomplished by anunevenness structure between the division core bobbins 20 when theneighboring bobbins 20 contact each other between a plurality of thedivision type core assemblies 300.

In this way, in order to form nine division cores u1-u9, v1-v9, andw1-w9 of each phase into three core groups G1-G3, G4-G6, and G7-G9, asshown in FIG. 5A, for example, it is necessary to sequentially wind thestator coil around nine division cores in the respective U, V, W phases.In the case that nine division cores u1-u9, v1-v9, and w1-w9 aresequentially wound in this manner, inconveniences caused by assemblingthe division type cores in the mold 31 without any positioningcomponents can be minimized.

Moreover, in the present invention, fixing grooves 34 a and 34 b forposition determination are formed in the mold 31. Since assemblypositions of the radial direction and the columnar direction of thedivision type core assembly 300 are automatically determined, anunskilled person in the art can do the assembly work and simultaneouslycan easily maintain the support state for the insert molding in thesubsequent processes. As a result, the assembly productivity is veryexcellent.

Moreover, the stator 3 comes close between the inner rotor 4 and theouter rotor 5 which are combined the inner and outer portions of thestator 3, but can maintain constant magnetic gaps G1 and G2, since theinner and outer flanges 30 b and 30 c of the division core 30 formincoming and outgoing curved surface at a predetermined curvature,respectively, and thus deviation from roundness of the inner and outercircumferential portions of a plurality of division type core assemblies300 becomes high.

In the meantime, FIG. 4A is a plan view of a division type skewed coreaccording to the present invention, and FIGS. 4B and 4C are a rear andplan views of a division type skew core in which a bobbin is combinedaccording to the present invention, respectively.

As shown in FIG. 4A, a division skewed core 36 according to the presentinvention is formed of generally an I-shape. As shown in FIGS. 4B and4C, a bobbin 200 which is made of an insulating material such as aplastic material is combined with the outer circumferential portion ofthe I-shaped division type skew core 36. The bobbin 200 is formed of arectangular box portion 210 around which a coil is wound and which isformed in the middle portion, and inner and outer flanges 220 a and 220b which are formed by being bent and extended from the inner and outersides of the rectangular box portion. The rectangular box portionbetween the flanges 220 a and 220 b is the space around which the coil33 can be wound.

In the I-shaped division type skewed core 36, the inner and outerflanges 36 b and 36 c are bent and extended to the inner and outer sidesof the linear type body 36 a, respectively. The inner flange 36 b isrounded inwards, so as to maintain a predetermined interval from theannular inner and outer rotors (not illustrated), and the outer flange36 c is rounded outwards. In this case, it is preferable that the outerflange 36 c has to be formed relatively larger than the inner flange 36b (FIG. 4A).

Moreover, it is preferable that the outer flange 220 b of the bobbin 200has to be formed relatively larger than the inner flange 220 a. In orderto fix the outgoing line of the coil 33 which has been wound around thebobbin, insertion grooves 26 a and 26 b for fixing coils are formed inthe upper portion of the inner and outer flanges 220 a and 220 b.Moreover, inner and outer protrusions 240 are integrally formed on theoutside of the lower portion of the inner and outer flanges 220 a and220 b, in order to guide a plurality of division type core assemblies300 so as to be automatically assembled into fixing grooves 34 a and 34b for positioning in the mold 31.

In the division skewed core 36, the skew is given in 0˜1 pitch rangedetermined inversely proportionally to the slot number (that is, thecore number) compared to the general division core in order to obtain aneffect of reducing cogging torque, noise, and vibration. In this case,one pitch is determined as 360°/slot number. For example, it is set upas 13.3° in the case the number of slots is twenty-seven.

The division skewed core 36 can secure a broader winding space incomparison with the structure of giving a skew to the integrated statorcore since the division skewed core 36 is a division type core and thusthe winding process of coils can be easily accomplished.

Furthermore, the core itself in the conventional division core forms thestructure of the motor. Accordingly, if a skew is given to theconventional division core, it is impossible to interconnect the core.However, it is possible to use a skew type division core in the presentinvention since a thermosetting resin can integrated in place of thestructure of the motor.

In the case of the division skewed core 36 according to the presentinvention, the coil winding and a plurality of division type coreassemblies around which coils are wound are injection-molded into theinsert molding mode, which is made identically to that of the divisioncore 30.

As described above, even though the present invention employs the skewedcore for the reduction of the cogging torque and the noise/vibration,the winding process of coils can be easily accomplished since it adoptsa division type core structure. Moreover, since each skewed core in thepresent invention is integrally molded by the insert molding mode usingthe thermosetting resin, the present invention can easily solve thedifficulties in the conventional division core in which the core itselfforms the structure of the motor.

Hereinbelow, a winding process for the division cores will be described.When a coil is sequentially wound around nine division cores u1-u9,v1-v9, and w1-w9, short jump wires J1 are secured between the adjacentdivision cores in the group, and long jump wires J2 are secured betweenthe groups of the division cores.

The forms and shapes of the division core 30 and the bobbin 20determines accommodating grooves in connection jigs for mutuallyconnecting and supporting the division cores to be described later.Accordingly, the type of the connection jigs is classified.

As shown in FIG. 7B, a continuous winding machine 46 of nine divisioncores, can be implemented using a general purpose winding machine havinga single spindle. The continuous winding machine 46 winds the statorcoil 33 around the bobbin 20, and includes a spindle 46 a forming therotational shaft of a spindle motor, a tailstock 46 c which is rotatablyinstalled in a transferable flow supporting portion 46 b which can moveto the left and right in the same axial direction as that of therotational shaft 46 e of the spindle 46 a, and supports the bobbinaround which the coil is wound, together with the spindle 46 a, andwhich includes the rotational shaft 46 e which rotates according torotation of the spindle 46 a, and a traverse device 46 d which suppliesthe coil 33 while moving in the space between the inner and outerflanges 22 a and 22 b of the bobbin 20 along the axial direction to theleft and right so that the coil is uniformly arranged and wound aroundthe bobbin when the bobbin is rotated according to rotation of thespindle 46 a. In FIG. 7B, a reference alphabetical numeral 46 f denotesa chucking lever which is installed at the head of the spindle 46 a andfixes the tip-end of the coil 33 which is withdrawn from the traversedevice, and reference alphabetical numerals 46 h and 46 g denotes dummyrollers, respectively.

When the continuous winding of the coil is performed using thecontinuous winding machine 46, the respective bobbins 20 a-20 i of thenine division cores 30 are firstly assembled into a core/jig assembly 45in which the cores and jigs are connected in series as shown in FIG. 7A,using eight connection jigs 40 a-40 c as shown in FIGS. 6A to 6D, andthen the assembled core/jig assembly 45 is set up in the continuouswinding machine 46 in order to wind the coil 33 around the nine bobbins20 a-20 i sequentially and continuously.

FIGS. 6A through 6C are a front view, a left side view, and a right sideview showing a connection jig connecting division type cores accordingto the present invention, respectively, and FIG. 6D is a cross-sectionalview cut along a line C-C of FIG. 6C.

As shown, in the case of a connection jig 40, inner and outer circularplates 41 and 42 are connected with each other through a connector 44keeping a predetermined distance therebetween, and inner and outeraccommodating grooves 41 b and 42 b into which inner and outer flanges22 a and 22 b of the bobbin 20 are inserted are formed on the inner andouter circular plates 41 and 42 in the opposite surfaces thereof,respectively. Moreover, a magnet 43 for fixing a pair of division cores30 respectively combined in the accommodating grooves is pressinglyinserted and coupled on the central portion of the connector 44 passingthrough both the accommodating grooves 41 b and 42 b.

Moreover, the left side surface of the inner circular plate 41 is madeof a flat shape excluding the accommodating groove 41 b, and the rightside surface thereof is made of inclined planes and a flat plane. Theleft side surface of the outer circular plate 42 is made of a flatshape, and the right side surface thereof is made of inclined planes anda flat shape excluding the accommodating groove 42 b.

The inner and outer accommodating grooves 41 b and 42 b include coreaccommodating grooves 41 c and 42 c for accommodating inner and outerflanges 30 b and 30 c of the division core 30 which is protruded fromthe inner and outer flanges 22 a and 22 b of the bobbin 20, and airexhaust grooves 41 d and 42 d.

Moreover, the inner and outer accommodating grooves 41 b and 42 b arearranged perpendicularly to each other. Inner and outer guide grooves 41a and 42 a for guiding the wound coil 33 to be passed over to the bobbinof the next stage are formed on the outer circumferential surfaceextended from the axis of the connection jig 40 in parallel with thelongitudinal direction of the inner and outer accommodating grooves 41 band 42 b.

The form and shape of the connection jig 40 are slightly different fromthose of the inner and outer flanges 30 b and 30 c of the division core30 and those of the inner and outer flanges 22 a and 22 b of the bobbin20. Accordingly, the forms and shapes of both the accommodating grooves41 b and 42 b differ from each other. That is, the accommodating groovesare classified into three types.

That is, as described above, the outer side surfaces of the inner andouter flanges 30 b and 30 of the division core 30 are formed of curvedsurfaces. Projections 24 a and 24 b which guide the division core to beautomatically assembled with positioning grooves 34 a and for positiondetermination in a mold 31 are protruded from the lower portion of theinner flange 22 a among the inner and outer flanges 22 a and 22 b of thebobbin 20. Moreover, the respective lengths from the flanges 30 b and 30c of the division core 30 to the top and bottom of the flanges 22 a and22 b of the bobbin 20, are formed so that the length up to the bottom ofthe flanges 22 a and 22 b of the bobbin 20 is longer than the length upto the top thereof.

Therefore, the connection jig 40 is classified into a first typeconnection jig 40 a in which the inner flange 22 a of the bobbin iscombined in one side accommodating groove 41 b, and the outer flange 22b of the bobbin is combined in the other side accommodating groove 42 b,a second type connection jig 40 b in which the inner flange 22 a of thebobbin is respectively combined in both the accommodating grooves 41 band 42 b, and a third type connection jig 40 c in which the outer flange22 b of the bobbin is respectively combined in both the accommodatinggrooves 41 b and 42 b.

In order to form a core/jig assembly 45, nine bobbins 20 a-20 i areassembled in series with eight connection jigs 40 a, 40 b, and 40 cwhich are made in the order of a second type-a third type-a first type-asecond type-a third type-a first type-a second type-a third type, asshown in FIG. 7A.

In the meantime, in the spindle 46 a of the continuous winding machine46 is formed an accommodating groove in which the outer flange 22 b ofthe bobbin is combined is formed. In a supporting shaft 46 b of thetailstock 46 c is formed an accommodating groove in which the innerflange 22 a of the bobbin is combined. The core/jig assembly 45 iscombined with and supported to both ends of the inner and outer theflanges 22 a and 22 b.

Then, when the coil is wound around the core/jig assembly 45, firstlythe core/jig assembly 45 rotates according to rotation of the spindlemotor and thus the coil 33 is wound around a first bobbin 20 a. In thiscase, the traverse device 46 d is moved to the right side by apredetermined set one pitch corresponding to the diameter of the coilwhenever the spindle 46 a is made to rotate once so that the coil 33 isuniformly wound in a rectangular box portion 21 between the inner andouter flanges 22 a and 22 b of the first bobbin 20 a. In this manner, ifthe stroke travel of the traverse device 46 d is sequentially made by apreviously set width of the bobbin, and the next spindle rotation ismade, the pitch movement of the traverse device 46 d is made in theopposite direction. That is, the coil winding is arranged one layer byone layer.

In this way, if a predetermined number of coil turns, for example, fiftycoil turns are wound, the spindle motor temporarily stops at theposition of the inner guide groove 41 a of the first connection jig 40b.

Then, after the traverse device 46 d is moved to the intermediateposition of a second bobbin 20 b as shown in FIG. 8A, the spindle 46 a,that is, the core/jig assembly 45 is made to rotate by 180° as shown inFIG. 8B. In the case that the core/jig assembly 45 is made to rotate,the coil 33 staying at the first bobbin 20 a moves to and is positionedthe second bobbin 20 b through the inner and outer guide grooves 41 aand 42 a of the first connection jig 40 b. Consequently, the short jumpwires J1 between the adjacent bobbins of the core group are secured.

Then, at the state where the traverse device 46 d is moved to theinitial position of the second bobbin 20 b, coil winding is performed byfifty coil turns identically with the coil winding of the first bobbin20 a. The spindle motor temporarily stops at the position of the innerguide groove 41 a of the inner circular plate 41 of the secondconnection jig 40 c. While securing the short jump wires J1 in the samemanner as that of the second bobbin 20 b, the traverse device 46 d movesto a third bobbin 20 c from the second bobbin 20 b, to thus complete thecoil winding.

Thereafter, as shown in FIG. 8C, the traverse device 46 d is moved tothe intermediate position of a fourth bobbin 20 d, and then the spindleis rotated by 90°. In the case that the 90° rotation is made, the coil33 staying at the third bobbin 20 c is moved to and position in theconnector 44 of the third connection jig 40 a through the inner guidegroove 41 a of the third connection jig 40 a. As shown in FIG. 8D, thetraverse device 46 d is again moved to the intermediate position of thethird connection jig 40 a, and the spindle 51 is rotated three times. Asa result, the long jump wires J2 is secured between the core group.

Thereafter, the traverse device 46 d is moved to the intermediateposition of the fourth bobbin 20 d, and then the spindle 51 is rotatedby 90°. In the case that the 90° rotation is made, the coil 31 stayingat the third connection jig 40 a is moved to and positioned in thefourth bobbin 20 d through the outer guide groove 42 a of the thirdconnection jig 40 a.

Then, the traverse device 46 d is moved to the initial position of thefourth bobbin 20 d, and the coil winding for the fourth to sixth bobbins20 d-20 f is sequentially performed, in the same manner as those of thefirst to third bobbins 20 a-20 c. Thereafter, the traverse device 46 dis moved from the sixth bobbin 20 f to the seventh bobbin 20 g, in thesame manner as the above-described manner and the coil winding for theseventh to ninth bobbins 20 g-20 f is sequentially performed, in thesame manner as that of the fourth to sixth bobbins 20 d-20 f.

Then, the coil 33 connected to the traverse device 46 d is cut, and thechucking about the coil at the start point is released. Thereafter, thecore/jig assembly 45 around which the coil has been wound is separatedfrom the continuous winding machine 46. If the division core 30, thatis, the bobbin is separated from the connection jig 40, three divisioncores u1-u3, u4-u6, and u7-u9 per each group are interconnected throughthe short jump wires J1 as shown in FIG. 5A. The division cores betweenthe respective groups of three groups G1˜G3 are interconnected throughthe long jump wires J2, to thereby obtain nine division cores u1-u9,v1-v9, and w1-w9.

In the above-described embodiment, the consecutive winding of the ninedivision cores which includes three division cores per each group hasbeen described using a general purpose winding machine equipped with thesingle spindle. However, the present invention is not limited thereto,but may be made in various forms.

Hereinbelow, the assembly process of the stator 3 will be describedbased on the division core according to the above-described firstembodiment of the present invention.

Firstly, a thermosetting resin, for example, a BMC (Bulk MoldingCompound) such as polyester is molded to the outside of the stator core30, excluding the inner and outer flanges 30 b and 30 c of the statorcore 30, to then form a bobbin 20 as shown in FIGS. 3B and 3C.

Then, the twenty-seven division cores u1-u9, v1-v9, and w1-w9 a areconnected in series as shown in FIG. 7A, nine by nine each electricalphase, using the connection jigs for connecting the division cores shownin FIGS. 6A to 6D, to thereby be assembled into a coil assembly 45. Thecoil 33 is sequentially and continuously wound around the respectivebobbins 20 a-20 i of the nine division cores by a coil continuouswinding method using the continuous winding machine 46, to therebyprepare three sets of coil assemblies 33 a-33 c having the short jumpwires J1 and the long jump wires J2, as shown in FIG. 5A.

Three sets of the coil assemblies 33 a-33 c are temporarily assembledinto the positioning grooves 34 a and 34 b for the positiondetermination which are formed in the annular grooves 32 of the mold 31for nine core groups G1-G9 in a mode that the core groups G1-G3, G4-G6,and G7-G9 of the respective phases are alternately arranged for eachphase in turn, as shown in FIG. 5B. Then, the coil assemblies areinsert-molded using the BMC (Bulk Molding Compound).

If the above-described insert molding is performed using the BMC (BulkMolding Compound) in order to cover the space between the respectivetwenty-seven division type core assemblies 300, and the upper/lowerwound coil portions and bobbins 20 excluding the outer opposing surfaceof the inner and outer flanges 30 b and 30 c of each division core 30,to thereby obtain an annular integrated stator 3 shown in FIGS. 2Athrough 2C.

In this case, it is preferable that if an extension 2 a is moldedaxially from the bottom of an annular stator supporter 2 which combinesand supports the division type core assemblies 300, it can be used forcoupling a housing 10, and plays a role of blocking the water leakedfrom a washing machine from flowing in into the motor.

Moreover, the conventional motor requires an additional insulator due toa high humidity environment of the washing time, at the time of mountingthe stator in a washing machine. However, since the present inventionuses the stator 3 of which the whole surface is molded with aninsulator, the additional insulator is not required. The sharp portionsdoing an assembly worker an injury are hidden in the outer surface ofthe stator, to thereby secure the safety.

Moreover, it is preferable that when a plurality of division type coreassemblies 300 are integrated, the coil 33 is wound around the bobbin 20of each core 30 and thus a plurality of coil ends each of a semi-circleshape are formed in the upper and lower portions of each division typecore assembly 300. If an injection molding is performed so that the BMCmolding is made in this shape, concavo-convex regions 2 p each of thesemi-circle shape are formed for each division type core assembly 300,as shown in FIG. 2A. As a result, the stator supporter 2 on the statorupper surface is formed to have a number of concavo-convex regions(unevenness) 2 p along a number of the division core assemblies 300around which coils 33 are wound.

Since the integrated stator 3 which has been injection-molded into thiskind of structure has been BMC-molded along a plurality of the coil endsof the semi-circle shape, the contact surface area contacting the airbecomes broad and heat dissipation is effectively done. Moreover, theturbulent flow occurs from the concavo-convex regions of the coil endsduring rotation of rotors 4 and 5, to thereby seek improvement of acooling performance.

Furthermore, as shown in FIGS. 2A and 2B, three mount positioning holes2 b and six bolt mounting holes 2 c are arranged at an equal intervalalong an axial extension 2 a, and a plurality of ribs 2 d which areformed in the surface where the mount positioning holes 2 b and the boltmounting holes 2 c are formed have an effect of improving an intensityduring mounting.

Moreover, a plurality of recesses 2 e formed by a plurality of the ribs2 d and the recess 2 f formed in the six bolt mounting holes 2 c createthe turbulent flow during rotation of the inner rotor 4 which isarranged in opposition to the recess 2 f to thereby improve a coolingperformance.

Furthermore, as shown in FIG. 2C, a plurality of large-size andsmall-size recesses 2 g and 2 h are formed in the rear side of thestator 3 by a plurality of the ribs 2 f. If a plurality of the ribs 2 fand a plurality of the large-size and small-size recesses 2 g and 2 hare formed by BMC, the thickness of BMC is formed into a thin plate, tothus reduce the weight at minimum, but increase the surface area andthus play a role of reinforcing a cooling efficiency.

Moreover, a plurality of the ribs 2 d and 2 f formed in the front/rearsurfaces of the stator 3 plays a role of blocking crack which can occurduring performing a BMC injection molding process from propagating.

In FIGS. 2A through 2C, a reference numeral 12 denotes a terminal blockfor supplying driving current to the stator coil 33 of a three phasedriving mode for example. A reference numeral 13 denotes a rotor 50which rotates in order to control the current supply for the stator coil33, that is, a hall integrated circuit (IC) assembly generating aposition signal for detecting the location of a magnet 4 a of the innerrotor 4.

C. Structure of Rotor and Manufacturing Process

FIGS. 10A through 10E are a perspective view of the upper side, apartially cut-out front view, a plan view, a rear view, and acircumferentially sectionalized perspective view of a rotor according tothe present invention, respectively. FIGS. 13A and 13B are a perspectiveview illustrating the inner and outer rotor assemblies and an involuteserration structure which are used for assembly of the double rotors ofthe present invention, respectively.

As shown in FIGS. 1A, 1B, and 10A through 10E, a BLDC motor according tothe present invention employs a structure of a double rotor 50 structurein which an inner rotor 4 where a plurality of magnets 4 a and aring-shaped inner yoke 4 b are arranged and an outer rotor 5 where aplurality of magnets 5 a and a ring-shaped outer yoke 5 b are arranged,are connected to the rotational shaft 9 through an involute serrationbushing 7 in the central portion by a rotor supporter 6.

As shown in FIG. 13A, in the case of the double rotor 50, a number ofmagnets which are segmented and magnetized in the outer side of theannular inner yoke 4 b into the N (North) pole and the S (South) pole,respectively, for example, twelve magnets 4 a are alternately arrangedusing an adhesive, to thereby form the inner rotor 4, and a number ofmagnets which are segmented and magnetized in the inner side of theannular outer yoke 5 b into the N (North) pole and the S (South) pole,respectively, for example, twelve magnets 5 a are alternately arrangedusing an adhesive, to thereby form the outer rotor 5. In this case, themagnets 4 a and 5 a which oppose the inner rotor 4 and the outer rotor 5are arranged in order to have the opposite polarities, respectively.

Then, the involute serration bushing 7 is disposed in the injection moldso as to be positioned at the centers of the inner rotor 4 and the outerrotor 5, and then is insert-molded using a thermosetting resin, forexample, BMC (Bulk Molding Compound) to thereby manufacture a rotor. Inthis case, the magnets of the inner rotor 4 and the outer rotor 5 areintegrally fabricated into an inner shape, so that the magnets can beplaced and fixed in the mold without undergoing any separate bondingprocess.

The inner rotor 4 and the outer rotor 5 are annularly molded at theouter surfaces thereof, excluding the opposite surfaces of magnets 4 aand 5 a facing each other at the time of an insert molding process, andthe involute serration bushing 7 is annularly molded at the overallouter surface thereof, excluding the axial direction. In order to makethe contact area wider in the axial direction, and enhance a couplingforce, a circular recess 70 a is formed in the middle of the outercircumferential surface of the bushing 7 in which a molding is made.Here, the outer circumferential surface 70 b is formed of a twelveangular surface having twelve edges. Moreover, the throughhole 70 c ofthe serration structure is formed in the central portion of the bushing7 in order to be serration-connected with the rotational shaft 9.

Moreover, the involute serration bushing 7, the inner rotor 4, and theouter rotor 5, by an insert molding process, are mutually connectedthrough a number of straight ribs which are radially extended from thecentral portion thereof, for example, twelve straight ribs 51, and anumber of straight ribs 51 are mutually connected between the involuteserration bushing 7 and the inner rotor 4, to then dispose a circularrib 52 therebetween in order to enhance a support stiffness.Consequently, a plurality of large-size and small-size holes 53 and 54are alternately formed in the portion facing the upper portion of thestator 3 along the circumferential direction owing to the mutualcrossing of the circular rib 52, the inner rotor 4, the outer rotor 5and a plurality of the straight ribs 51.

Furthermore, as shown in FIG. 10A, a number of grooves 6 b areperiodically formed in an annular molding support 6 a supporting theinner rotor 4 among the rotor supporters 6. A plurality of large-sizeholes 53 including the recesses 6 b play a role of a path through whichthe external air passes to the inner side of the inner rotor 4 and bothsides of the magnetic gaps G1 and G2 as shown in FIG. 11C. Consequently,when the rotor 50 is rotated, the externally generated wind istransferred to the inner and outer magnets 4 a and 5 a and the stator 3through the large-size holes 53, to thereby improve a coolingperformance.

That is, the wind which enters the large-size holes 53 is discharged outthrough the inner side of the inner rotor 4 and the magnetic gaps G1 andG2 like the airflow of FIG. 11C. Further, the wind which enters thesmall-size holes 54 is discharged out through the magnetic gaps G1 andG2 like the airflow of FIG. 11B. In this case, the large-size holes 53are preferably made to enlarge the cross-sectional area of the straightrib 51 perpendicularly to the circumferential direction duringmanufacturing the holes to thus improve a cooling effect. Further, thelarge-size holes 53 play a role of a window with which a user is capableof confirming the inner magnetic gap G1.

Consequently, the top of the stator 3, the space S opposing each otherin the connectors between the inner and outer rotors 4 and 5, and theclosed space like the magnetic gaps G1 and G2 of the inner and outerrotors 4 and 5 and the stator 3 are open to thereby enhance the coolingperformance due to the double rotor structure.

Moreover, a plurality of sections which are formed owing to a pluralityof the straight line ribs 51, the circular rib 52, and the annularmolding supporter 6 a generate the turbulent flow at the time ofrotation of the rotors, to thereby improve the cooling performance,since the recesses 55 are formed on the top and bottom of the inner andouter side surfaces, and further due to the difference of the windentering the large-size and small-size holes 53 and 54 which arealternately arranged.

In the meantime, it is necessary to employ a heat dissipation/coolingstructure in especially, the rotor 50 in order to emit and cool the heatwhich is generated from the coil and the magnets due to the loss of theelectric and magnetic force, by the driving current applied in thestator coil 33 at the time of driving the motor.

In the present invention, because the rotor 50 is manufactured with thethermosetting resin, it is easy to manufacture cooling blades (calledfan blades) for heat dissipation in various forms. For example, variousshapes of cooling blades 59 which can generate wind for the inner rotor4, the outer rotor 5, or both rotors 4 and 5 are integrally fabricated,so that the cooling effect of the rotor 50 and the stator 3 can beimproved.

For example, since the cooling blades formed on the lower surface of theouter rotor 5 face the radial direction firstly as shown in FIG. 12A, aplurality of straight fans 60 can be used in which the angle formed by areference line is 0°. Moreover, as shown in FIG. 12B, the cooling bladesform the angle of 0° with respect to the reference line, but can adopt astructure of a plurality of Sirocco fans 62 where the circular recessesare formed along the rotational direction of the rotor to therebygenerate a large amount of wind, or a structure of a plurality of turbofan 63 where the recesses are formed into the opposite direction to therotational direction of the rotor.

Furthermore, as shown in FIG. 12C, the cooling blades can adopt astructure of a plurality of rake-type fans 61 which are rotated by apredetermined angle α in the radial direction. That is, −90°≦α≦+90°.Moreover, the cooling blades can adopt a structure of a plurality ofcurved fans 64 of which the shapes of the fans are curved, and whichform a predetermined angle α with respect to the reference line in theradial direction as shown in FIG. 12D. However, it is possible that thecooling blades can adopt a structure of streamlined shape fans 65 shownin FIG. 12E. Moreover, the cooling blades can be formed of a pluralityof triangle fans 66 having the form of a substantially right-angledtriangle between the outer bottom side surface of the outer rotor 5 andthe flange thereof as shown in FIG. 10A.

Consequently, a plurality of cooling blades (or fan blades) integrallyformed in the lower surface of the outer rotor 5, perform air coolingvoluntarily for the stator 3 at the time of rotation of the rotor 50.

As described above, the integrated double rotor 50 according to thepresent invention does not need a separate support plate, because aplurality of magnets 4 a and 5 a in the inner rotor 4 and the outerrotor 5 haven been integrated with a BMC (Bulk Molding Compound) rotorsupporter 6 having a basic structure intensity.

Moreover, in the present invention, a plurality of magnets 4 a and 5 aare fixed to the inner and outer yokes 4 b and 5 b, primarily by anadhesive. The BMC rotor supporter 6 additionally fixes magnets 4 a and 5a as shown in FIG. 10B. In that way, the scattering and positionalmovement of the magnets 4 a and 5 a by the centrifugal force can befundamentally prevented. In this case, such an effect of preventing thescattering and positional movement of the magnets can be furtherenhanced by giving the chamfer 4 c to the opening surface of the magnets4 a and 5 a.

Consequently, in the motor of the conventional inner rotor typestructure, the additional components are required for theanti-scattering of the magnets, but the anti-scattering of the magnetscan be solved by the BMC rotor supporter 6 in the present invention.Moreover, in the present invention, the magnets 4 a and 5 a and theinner and outer yokes 4 b and 5 b are surrounded by the BMC rotorsupporter 6. Therefore, the damage of the magnets 4 a and 5 a which canoccur at the assembly time of the stator 3 and rotor 50 can beprevented.

Moreover, since a plurality of magnets 4 a and 5 a of the inner rotor 4and the outer rotor 5 are concentrically arranged by the insert molding,a deviation from roundness becomes high. Accordingly, when the rotorsare assembled with the stator 3, it is possible to maintain the uniformmagnetic gap.

In the case of the above-described BLDC motor 1 of the radial core type,the rotor 50 of the double rotor structure is rotated as the drivingcurrent is applied to the coil 33 of the stator 3. In this case, in thepresent invention, magnets 4 a and 5 a in the inner rotor 4 and theouter rotor 5 and the division core 30 in the division type coreassembly 300 form one complete magnetic circuit which follows the arrowflow of FIG. 1B. Therefore, it is possible to make the perfect divisionof the stator core.

That is, as shown in FIG. 1B, in the present invention having thedivision type core structure, a magnetic circuit is formed according tothe arrow flow following the direction of the magnet 4 a of the innerrotor 4, the inner yoke 4 b, the magnet 4 a, the division core 30, themagnet 5 a of the outer rotor 5, the outer yoke 5 b, and the divisioncore 30.

As described above, in order to form the magnetic circuit and have theperfect division core structure, it is necessary to make the progressingof the magnetic flux face the magnetic gaps G1 and G2. For this purpose,the interval between the adjacent division cores 30 is set wider thanthe magnetic gaps G1 and G2 between the rotors 4 and 5 and the stator 3.

Therefore, in the present invention, it is possible to make the statorcore into a plurality of division cores 30. When the double rotor 50 isemployed, the motor output and torque can be moreover increased comparedwith the motor of the single rotor.

Moreover, since the size of the division core 30 is small, the wastagerate of the silicon steel lamination becomes small and thus the materialloss does not nearly exist and the shape thereof is simplified, tothereby make the manufacture easy. It is moreover possible that thewinding around the division core 30 can be performed using a generalpurpose winding machine and thus the investment cost for a coil windingcost and a winding facility is reduced.

Furthermore, in the above-described embodiment, since the rotor and thestator are integrated using the resin, a durability, a moisture proofproperty, etc., are excellent and it is suitable for a drum drivingsource for a washing machine used in a high humidity environment but isnot thus limited thereto. Moreover, it is possible to modify a mountingstructure of the stator, according to an apparatus where a motor isapplied.

II. Second Embodiment

Hereinbelow, the BLDC motor of the radial core type having a structureof double rotors according to a second embodiment of the presentinvention will be described.

FIG. 14 is an axial sectional view of a BLDC motor of a radial core typehaving a structure of double rotors according to a second embodiment ofthe present invention. FIG. 15A is a plan view of double rotors shown inFIG. 14. FIGS. 15B and 15C are a cross-sectional view and a rear view ofthe double rotors of FIG. 15A which is cut along a line X-X,respectively. FIG. 16A is a plan view of a stator shown in FIG. 14.FIGS. 16B and 16C are a cross-sectional view and a rear view of thestator of FIG. 16A which is cut along a line Y-Y.

Referring to FIG. 14, the BLDC motor 100 of the radial core type doublerotor structure according to the second embodiment of the presentinvention includes a stator 330 in which a plurality of division cores30 are integrally formed by an annular stator supporter 2 which ismanufactured by an insert molding method using a thermosetting resinafter coils have been wound around the outer circumference of bobbins(not shown), an inner rotor 4 which has predetermined magnetic gaps G1and G2 on the inner and outer circumferential portions of the stator 330in which a plurality of magnets 4 a and ring-shaped inner yokes 4 b aredisposed in an annular form, an outer rotor 5 in which a plurality ofmagnets 5 a and ring-shaped outer yokes 5 b are disposed, and arotational shaft 9 whose one end is connected to the central portion ofa rotor supporter 6 through an involute serration bushing 7 and whoseother end is rotatably supported through bearings 8 a and 8 b, which issame as that of the first embodiment.

In the stator 330, a plurality of the division cores 30 which have beencompletely division type are integrally molded by an annular statorsupporter 2 in an annular form. The stator supporter 2 includes anextension 2 a extended toward the inner side thereof. The statorsupporter 2 is supported by an anchoring bolt 11 at predeterminedpositions set by positioning holes or pins in for example, the housing10 of a washing machine.

In addition, the inner rotor 4 and the outer rotor 5 in a double rotor500 according to the second embodiment of the present invention areconnected with the rotational shaft 9 through the involute serrationbushing 7 on the central portion of the rotor supporter 6. The magnets 4a and 5 a facing each other in the inner rotor 4 and the outer rotor 5are disposed to have opposite polarities to each other.

Moreover, the rotational shaft 9 is rotatably supported by a pair ofbearings 8 a and 8 b which are spaced at a predetermined distance in thehousing. In order to prevent the rotor 500 from being separated, a platewasher 17, a spring washer 18, and a fixing nut 14 are sequentiallyengaged with the rotor 500. Moreover, a plate washer screw nut 15 isconnected with the rotational shaft 9 in the outer side of the firstbearing 8 a, in order to prevent the first bearing 8 a from beingseparated from the housing.

Therefore, the BLDC motor 100 of the second embodiment is also comprisedof the double rotor 500 in which the inner rotor 4 and the outer rotor 5are supported by the rotor supporter 6, and the single stator 330. Theconfiguration of the magnetic circuit and principles in operation of themotor are identical with those of the first embodiment.

The second embodiment will be illustrated below with respect to thedifferences from the first embodiment.

The BLDC motor 100 of the second embodiment differs from that of thefirst embodiment. That is, the axial connector 160 of the rotor 500combined with the rotational shaft 9 as shown in FIG. 14 is disposed thecenter of gravity of the rotor 500, in the rotor supporting structure,which can suppress the noise occurrence and vibration to the minimum bymaintaining the rotational equilibrium at the time of rotation of therotor 500.

That is, the axial connector 16 of the rotor 50 combined with therotational shaft 9 in the first embodiment deviates a little bit fromthe center of gravity of the rotor 50 along the axial direction. Theaxial connector 16 is comprised of a bushing 7 combined with therotational shaft 9, and a bushing supporter 7 a made of a resinsurrounding the bushing 7. The bushing supporter 7 a is connected withthe top of the rotor supporter 6 which integrally supports the inner andouter rotors 4 and 5 through a plurality of straight ribs 51.

Therefore, the bushing 7 delivering the rotational force of the rotor 50to the rotational shaft 9 is located at the spot which deviates a littlebit from the centroid of the rotor 50 along the axial direction in thefirst embodiment. Consequently, a deviation exists between the centersof magnets 4 a and 5 a and yokes 4 b and 5 b substantially determiningthe centroid of the rotor, and the center of the bushing 7. Thus,occurrence of the noise and vibration cannot be suppressed, and thepower transmission efficiency is reduced.

In the meantime, in the second embodiment, the bushing 7 is combinedwith the rotational shaft 9, and the bushing 7 is supported by thebushing supporter 7 b made of the thermosetting resin by the insertmolding. The bushing supporter 7 b is connected to the in-between of therotor supporter 6 supporting the inner rotor 4 through a plurality ofstraight ribs 510 extended radially from the top of the bushingsupporter. Consequently, the bushing 7 and the bushing supporter 7 a arepositioned in the centroid of the rotor 500.

Therefore, in the BLDC motor 100 of the second embodiment, and the axialconnector 160 of the rotor 500 combined with the rotational shaft 9 isarranged in the centroid of the rotor 500 thereby maintaining therotational equilibrium at the time of rotation of the rotor 500, andthus suppress occurrence of noise and vibration to the minimum, andenable an efficient power transmission. Moreover, the axial length ofthe motor can be shortened to the minimum in the case the axialconnector 160 of the rotor 500 is arranged in the centroid of the rotor500.

Moreover, as shown in FIGS. 15A to 15C, similarly to the double rotor 50of the first embodiment, the inner rotor 4 and the outer rotor 5 in thedouble rotor 500 of the second embodiment are integrated by the rotorsupporter 6 in the form of an inverse “U” shape. The rotor supporter 6and the involute serration bushing 7 are mutually connected throughtwelve straight ribs 510 radially extending from the central portion ofthe double rotor. Also, the involute serration bushing 7 and the innerrotor 4 a are mutually connected through a plurality of straight ribs510. In order to enhance the support intensity, the circular rib 520 isarranged in connection with a plurality of the straight ribs 510.

Moreover, a plurality of large-size holes 530 and a plurality ofsmall-size holes 540 for cooling the stator 330 located in the inside ofthe rotor 500 are alternately formed along the circumferential directionat portions facing the rotor supporter 6 and the upper portion of thestator 3. In this case, the recesses 600 b are periodically formed inthe annular molding supporter 600 a supporting the inner rotor 4 alongthe circumferential direction as shown in FIG. 15A.

Furthermore, in the rotor 500 of the second embodiment, in comparisonwith the first embodiment, the supporting structure of a plurality ofstraight ribs 510 connecting between the bushing 7 and the inner rotor 4is of a depression structure which is moved to the inner side of therotor. Accordingly, the recesses 600 b are arranged at the locationwhere the top portion of the stator 330 and part of the inner side ofthe stator 330 are opened to the outside. A plurality of the large-sizeholes 530 including the recesses 600 b form a wider path through whichthe external air passes through the inner side of the inner rotor 4 andboth sides of the magnetic gaps G1 and G2. Consequently a more excellentcooling effect is obtained in comparison with that of the firstembodiment.

Consequently, the large-size holes 530 delivers the externally generatedwind to the inner and outer magnets 4 a and 5 a and the stator 330, whenthe rotor 500 is rotated. In addition, the wind which enters thesmall-size holes 540 passes through the magnetic gaps G1 and G2, tothereby improve a cooling performance.

Consequently, due to the double rotor structure, the closed spaces suchas the top of the stator 3, the space S facing the connection portionbetween the inner and outer rotors 4 and 5, and the magnetic gaps G1 andG2 of the inner and outer rotors 4 and 5 and the stator 3 are opened tothereby improve the cooling performance.

Moreover, the recesses 550 are formed in the upper and lower surfaces ofthe inner and outer sides of a plurality of sections which are formedowing to a plurality of straight ribs 510, the circular ribs 520, andthe annular molding supporter 600 a. Further, due to the difference ofthe wind entering the large-size and small-size holes 530 and 540 whichare alternately disposed, a turbulent flow is generated at the time ofrotation of the rotor, to thereby improve the cooling performance.

In the meantime, the rake-type cooling blades 59 are integrally includedon the bottom of the outer rotor 5 in the rotor 500 of the secondembodiment, in order to perform the heat dissipation/cooling.

According to an environment under which the motor is applied, theindividual shapes as well as the overall shape the cooling blades 59should be appropriately designed to optimize the flow of the air and theair volume so as not to exceed the maximum allowable temperature whenthe maximum load is applied to the motor. For example, in the case thatthe motor is applied to a full-automatic washing machine, the low speedforward and reverse rotations are repeated during performing a washingcourse. Only a high speed forward rotation (or a high speed reverserotation) should be performed during performing a dehydration course.Therefore, when the motor performs a long time washing course and thusperforms the high speed forward rotation to perform the dehydrationcourse at the state where the motor reaches a temperature to someextent, the motor reaches the maximum load and maximum temperature.Accordingly, it is preferable that the cooling blades 59 also have a fanstructure of enhancing the cooling effect when the high speed forwardrotation of the motor is made.

In the meantime, as shown in FIGS. 16A to 16C, in the stator 330 of thesecond embodiment similarly to the first embodiment, a plurality ofdivision cores 30 are manufactured by winding the coil 33 around thecircumference of the bobbin (not shown) and then insert-molding the coil33 using the thermosetting resin. Consequently the coil 33 is integrallyformed with the stator supporter 2 in an annular form.

In this case, in the stator 330 of the second embodiment, instead offorming the thickness of the stator supporter 2 into the thin plate asshown in FIGS. 16B and 16C, when the stator is molded using thethermosetting resin, annular ribs 2 j and 2 k are formed at the innerand outer sides of the stator, and a plurality of band form ribs 2 leach having a predetermined length on the middle of annular ribs 2 j and2 k are formed at the inner and outer sides thereof. Therefore, thestator 330 blocks the crack from propagating, which can occur at thetime of the injection molding by forming the ribs 2 j-2 l, reducing theweight to the minimum, increasing the surface area, making the coolingefficiency high, and reinforcing the intensity.

Furthermore, as shown in FIGS. 16A to 16C, three mount positioning holes2 b and six bolt mounting holes 2 c are arranged at an equal intervalalong an axial extension 2 a, and three mount positioning pins 2 i areformed in one side of the bolt mounting holes 2 c at an equal interval.

Therefore, when the motor 100 is assembled in the housing 10 of thewashing machine, the mount positioning hole 2 b of the axial directionextension 2 a is made to be congruent with the mount positioning pin 16,and then a washer is interposed in the bolt mounting hole 2 c to tightenthe anchoring bolt 11, in the case that the mount positioning pin 16 isplanted in the housing 10 as a reference for determining the mountinglocation of the stator, as shown in FIG. 1A. However, on the contrary,in the case where the mount positioning hole is formed in the housing10, the mount positioning pin 2 i of the above-described axial directionextension 2 a is made to be congruent with the mount positioning hole,and then a washer is interposed in the bolt mounting hole 2 c to therebytighten the anchoring bolt 11. In this case, preferably, the bushing 2 mis inserted into the bolt mounting hole 2 c, to endure the strongcoupling force of the anchoring bolt 11.

Taking this point of view into consideration, the stator 330 of thesecond embodiment includes the mount positioning hole 2 b, the six boltmounting holes 2 c, and the three mount positioning pins 2 i in theaxial extension 2 a.

Moreover, as shown in FIG. 16A, in the upper surface of the axialextension 2 a are formed a plurality of recesses 2 e formed owing to aplurality of ribs 2 d and the recesses formed in periphery of six boltmounting hole 2 c, in the same manner as that of the first embodiment.The plurality of recesses 2 e formed owing to a plurality of ribs 2 dand the recesses formed in periphery of six bolt mounting hole 2 ccreates the turbulence at the time of rotation of the inner rotor 4, tothereby improve the cooling performance.

Furthermore, as shown in FIG. 16C, a plurality of large-size andsmall-size recesses 2 g and 2 h are formed even in the rear side of thestator 3 by a plurality of ribs 2 f. Accordingly, the thickness of thestator assembly 2 is made of a thin plate, so as to reduce the weight tothe minimum, increase the surface area, make the cooling efficiencyhigh, and reinforce the intensity.

The above-described second embodiment employs a depression typesupporting structure that the axial connector of the rotor combined withthe rotational shaft is disposed at the centroid of the inner side ofthe rotor. However, it is possible to support the axial connector of therotor in the first embodiment in the form of a depression typestructure.

Moreover, the first and second embodiments illustrated in the presentinvention have been described with respect to the drive motor foroperating the washing machine for example, but the present invention canbe modified to drive the other apparatuses such as radiators forvehicles.

As described above, in the present invention, the radial core type BLDCmotor employs the double rotor structure. Accordingly, when the statorcore is formed into the perfectly division cores, using the positioningstructure formed in the mold itself, a plurality of division type coreassemblies are automatically positioned and then injection-molded usingthe thermosetting resin by an insert molding mode. As a result, aseparate core support plate is not used to assemble a plurality ofdivision cores to thereby enhance an assembly productivity of stators.

Moreover, in the double rotor structure of the present invention, thecooling aperture is formed so that the cross-sectional area of thecooling aperture is as broad as possible which is perpendicular in thecircumferential direction with the rotor supporter and the rib whichconnect the inner and outer rotors and the bushing. The cooling apertureis designed to alternately vary in size in turn. Accordingly, thesupport intensities of the rotor supporter and the rib are reinforced,and simultaneously a large amount of wind is generated to thus createthe turbulent flow. The flow of the cooled air can be induced to theupper space of the stator and the magnetic gap between the inner andouter rotors and the stator and thus the heat generated from the rotorsand the stator can be effectively cooled.

Furthermore, in the structure of the stator of the present invention,the contact area to the air is increased by forming a supporter using aresin along the semicircular curved surface of the coil which is woundaround the bobbin when the stator is integrally molded using athermosetting resin, and the turbulent flow is generated at the time ofrotation of the rotor to thus improve the cooling performance. Aplurality of bolt mounting holes and mounting positioning holes forfixing the stator and a plurality of throughholes formed by a pluralityof radial ribs are included in the bearing housing, to thereby maintainthe proper support intensity, reduce the material cost, seek the lightweight, and produce the turbulence together with the cooling blades ofthe inner rotor at the time of rotation of the rotor, and to thusimprove the cooling performance.

Moreover, in the present invention, one coil is consecutively woundaround a plurality of division type stator cores corresponding to eachphase by a continuous winding method and mutually connected. That is,when the stator cores are positioned on the mold, inconveniences thatcan be caused by the absence of the separate positioning component canbe minimized.

Further, the present invention provides a BLDC motor including a skewcore structure stator in which a coil winding process is easy since adivision type core structure is employed even though the skew corestructure has been employed, and each skew core can be integrally moldedin an insert molding process using a thermosetting resin so as to beeasily assembled, thereby reducing a cogging torque and noise/vibration

Furthermore, in the present invention, the axial connector of the rotorcombined with the rotational shaft is disposed at the centroid of theinner side of the rotor, to thus suppress generating of vibration atminimum at the time of rotation of the rotor, and to thus improve thecooling efficiency of the stator and the rotors.

Moreover, the present invention integrally molds the double rotor andstator by an insert molding process using the thermosetting resin, tothereby heighten a durability, reliability, and a water-proofperformance. The thermosetting resin surrounding the double rotor andthe stator is a heat-resistant material which can endure up to 600° C.,to thereby heighten the safety from the fire hazard.

As described above, the present invention has been described withrespect to particularly preferred embodiments. However, the presentinvention is not limited to the above embodiments, and it is possiblefor one who has an ordinary skill in the art to make variousmodifications and variations, without departing off the spirit of thepresent invention.

1. An apparatus for driving a drum or a tub for holding clothes to bewashed in a washing machine comprising: a housing in the washingmachine; a rotational shaft is rotatably mounted in the housing of thewashing machine, wherein the drum or the tub is connected to a frontportion of the rotational shaft projected into the housing; anintegrated double rotor including an inner rotor and an outer rotor inwhich a plurality of N-pole and S-pole magnets are disposed alternatelyin annular form on different concentric circumferences in each rotor,and opposing magnets with a predetermined distance between the inner andouter rotors are disposed to have opposite polarities, and a rotorsupporter molded using a thermosetting resin, so that the respectiveinner and outer rotors are annularly integrated, a trench space isformed between the inner rotor and the outer rotor, and an end extendedfrom the inner rotor to the central portion is connected with the outercircumferential surface of a bushing combined with the rotational shaft;and an integrated stator wherein U, V, W phase coil assemblies formed ofa number of core groups including a number of independent division coreson the outer portion of which bobbins are respectively formed, whereinfor each phase coil assembly, coils are sequentially wound around eachdivision core so that short jump wires are connected between thedivision cores in each division core group, and long jump wires areconnected between the division core groups, wherein the division coregroups of the U, V, W phase coil assemblies are alternately disposed inan annular form in sequence of the phases, wherein the respectivedivision core groups are integrally formed into a single body in annularform by a stator support, and wherein one end of the integrated statoris disposed in the trench space between the inner and outer rotors andan extension axially extended from the other end of the integratedstator is fixed to the housing of the washing machine.
 2. The drivingapparatus of claim 1, wherein said rotor supporter comprises: a numberof large-size holes and small-size holes alternately disposed in orderto guide external air to the trench space opposing an end of the statorbetween the inner and outer rotors in the inner side direction of theinner rotor and in a magnetic gap direction between the inner and outerrotors and the stator, and a number of radial ribs disposed as axialcouplers surrounding the outer circumferential surface of the bushingfrom the inner rotor to the central portion thereof.
 3. The drivingapparatus of claim 2, wherein a number of grooves are periodicallyformed at portions where an annular molding support supporting the innerrotor among the rotor supporters, meets a number of the large-size holesalong the circumferential direction.
 4. The driving apparatus of claim2, wherein said axial coupler is disposed in a center of gravity of thedouble rotor.
 5. The driving apparatus of claim 1, wherein the rotor ofthe motor further comprises a number of cooling blades integrally formedwith the rotor supporter at the lower portion of the inner rotor and/orouter rotor for producing wind during rotation of the rotor.
 6. Thedriving apparatus of claim 1, further comprising: a number of coolingblades integrally formed on the outer circumferential surface of theouter rotor, for producing wind during rotation of the rotor.
 7. Thedriving apparatus of claim 1, wherein a number of grooves formed by anumber of ribs are included in the axial extension of the stator supportin order to produce a turbulent flow during rotation of the rotor tothus enhance a cooling performance, and a number of positioning holesand protrusions, and a number of bolt fitting holes are periodicallydisposed in the grooves at equal intervals in order to determine anassembly position when the stator is mounted in the housing of thewashing machine.
 8. The driving apparatus of claim 1, wherein the statorsupport on the stator upper surface is formed to have a number ofconcavo-convex regions along a number of the division core assemblyshapes around which coils are wound so that heat can be emitted via alarge contact surface area.
 9. The driving apparatus of claim 1, whereinfor each phase coil assembly, the division core groups of the U, V, Wphase coil assemblies are alternately disposed in an annular form insequence of the phases.
 10. The driving apparatus of claim 1, whereinsaid bobbins for a number of the independent division cores comprisesfirst and second coupling protrusions coupled with a number of pairs ofpositioning fixing grooves formed in opposition to the inner and outerwalls of annular grooves when the bobbins are temporarily assembled intothe annular grooves in the mold for an insert molding.
 11. The drivingapparatus of claim 1, wherein said stator coil is made of Cu or Al. 12.An apparatus for driving a drum or a tub for holding clothes to bewashed in a washing machine comprising: a housing in the washingmachine; an integrated double rotor including an inner rotor and anouter rotor in which N-pole and S-pole magnets of twenty-four poles aredisposed alternately in an annular form on different concentriccircumferences in each rotor, and opposing magnets with a predetermineddistance between the inner and outer rotors are disposed to haveopposite polarities, and a rotor supporter molded using a thermosettingresin, so that the respective inner and outer rotors are annularlyintegrated, and a trench space is formed between the inner rotor and theouter rotor, so that the rotor supporter is extended from the innerrotor to an axial coupler surrounding a bushing; a rotational shaftwhose one end is coupled with the bushing and other end is rotatablymounted in the housing of the washing machine, wherein the drum or thetub is connected to a front portion of the rotational shaft projectedinto the housing; and an integrated stator wherein U, V, W phase coilassemblies formed of a number of core groups including a number ofindependent division cores on the outer portion of which bobbins arerespectively formed, wherein for each phase coil assembly, the divisioncore groups of the U, V, W phase coil assemblies are alternatelydisposed in an annular form in sequence of the phases, wherein therespective division core groups are integrally formed into a single bodyin annular form by a stator support, wherein one end of the integratedstator is disposed in the trench space between the inner and outerrotors, and wherein a number of division cores respectively included inthe U, V, W phase coil assemblies are mutually connected by thesequentially wound coils.
 13. The driving apparatus of claim 12, whereinsaid stator is made by an insert molding method using a thermosettingresin at a temporary assembled state, in which a number of core groupsincluding a number of division cores adjacent to each other are disposedin a mold having a number of pairs of positioning fixing groovesalternately correspondingly formed in sequence of the phases.
 14. Thedriving apparatus of claim 12, wherein said rotor supporter comprises: anumber of large-size holes and small-size holes alternately disposed inorder to guide external air to the trench space opposing an end of thestator between the inner and outer rotors in the inner side directionthe inner rotor and in a magnetic gap direction between the inner andouter rotors and the stator, and a number of radial ribs disposed asaxial couplers.
 15. An apparatus for driving a drum or a tub for holdingclothes to be washed in a washing machine comprising: a housing in thewashing machine; an integrated double rotor including an inner rotor andan outer rotor in which a plurality of N-pole and S-pole magnets aredisposed alternately in annular form on different concentriccircumferences in each rotor, and opposing magnets with a predetermineddistance between the inner and outer rotors are disposed to haveopposite polarities, and a rotor supporter molded using a thermosettingresin, so that the respective inner and outer rotors are annularlyintegrated, and a trench space is formed between the inner rotor and theouter rotor, so that the rotor supporter is extended from the innerrotor to an axial coupler surrounding a bushing; a rotational shafthaving one end coupled with the bushing and two points of the other endrotatably mounted in the housing of the washing machine, wherein thedrum or the tub is connected to a front portion of the rotational shaftprojected into the housing; and an integrated stator wherein for eachphase, coils are sequentially wound around each division core in asequential winding method, wherein the respective division cores areintegrally formed into a single body in an annular form by a statorsupport, wherein one end of the integrated stator is disposed in thetrench space between the inner and outer rotors and an extension axiallyextended from the other end of the integrated stator is fixed to thehousing of the washing machine, and wherein said axial coupler isdisposed in the center of gravity of the double rotor, wherein saidrotor supporter comprises: a number of large-size holes and small-sizeholes are alternately disposed in order to guide external air to arecess space opposing an end of a stator between the inner and outerrotors in the inner side direction the inner rotor and in a magnetic gapdirection between the inner and outer rotors and the stator, and anumber of radial ribs disposed as axial couplers surrounding the outercircumferential surface of the bushing from the inner rotor to thecentral portion thereof.
 16. The driving apparatus of claim 15, whereinthe rotor of the motor further comprises a number of cooling bladesintegrally formed with the rotor supporter at the lower portion of theouter rotor for producing wind during rotation of the rotor.
 17. Thedriving apparatus of claim 15, wherein a number of the division coresare skewed.
 18. The driving apparatus of claim 15, wherein the intervalbetween the adjacent division cores is set wider than the magnetic gapbetween the inner and outer rotors and the stator.